Moult Strategies of Four Species of Grassfinches Living in the Same Area

Abstract

Moult of the remiges was studied over a period of two years in sympatric populations of the Red-browed Firetail Emblema temporalis, the Diamond Firetail E. gunata, the Double-barred Finch Poephila bichenovii and the Plum-headed Finch Aidemosyne modesta from the central western slopes of New South Wales. Primary and secondary moult-rates were calculated from individuals captured more than once during the same moult and the mean duration of primary and secondary moult was estimated by multiplying the rate by the score of the completed moult. There were significant differences within and among species, years and sites. P. bichenovii moulted at the slowest primary and secondary rate and continued its moult throughout winter at an even slower rate. This moult-strategy may be non-adaptive for populations in New South Wales. E. temporalis had variable primary moult-rates compared between years and sites, which may reflect food supply and climate; no significant differences could be found between the secondary rates. The rates of A. modesta were characterised by a fast primary and a slow secondary moult which could be adaptive for regular seasonal movements. E. guttata replaced both primaries and secondaries at a fast rate in both years and represented a more conventional moult pattern. Among species there was more variation in the rates of primaries than of secondaries. Moulting seasons were highly synchronised in both years and fairly constant. Moult occurred from November until May, except for P. bichenovii. Moult and breeding overlapped in all four species and a high proportion of birds caring for eggs or nestlings actively replaced remiges.